Electronic surface states in superlattice with complex basis

The electronic structure of a semi-infinite superlattice (SL) with a complex basis consisting of two identical wells coupled via two different barriers is investigated. The possibility of the surface state existence for a periodic termination of the SL potential (i.e., without perturbing the SL potential at the surface) is shown for such a two-barrier basis, in contrast to the conventional one of single well and barrier. This main conclusion is based on analytical considerations, however, some numerical results for the GaAs/AlAs SL are also presented.